Display device with deformable reflective medium

ABSTRACT

A display device having a transparent supporting plate which is provided with transflective regions. At a short distance from the first supporting plate resilient electrodes are connected which are manufactured from a partially reflective material. By varying the distance between the resilient electrodes and the transflective regions, the reflection of incident light can be controlled from zero to maximum intensity as a result of the occurring interference. Both monocolor and multicolor pictures can be displayed by means of such a display device. Such a display device is particularly suitable for use in a projection television device.

The invention relates to a display device comprising a transparent firstsupporting plate having a transflective layer, and a partiallyreflective layer which reflects to substantially the same extent as thetransflective layer and which is spaced apart from the transflectivelayer and which is secured so as to be movable to the first supportingplate in such manner that when light is incident on the device,interference phenomena occur dependent on the distance between thetransflective layer and the partially reflective layer. By atransflective layer is meant a layer which partially transmits andpartially reflects impinging light.

The invention also relates to a method of manufacturing such a displaydevice. The invention further relates to a data processing device and toa projection television device having such a display device.

Such a display device is disclosed in U.S. Pat. No. 2,534,846. In thisdevice an incident light beam is partly reflected and partly transmittedby the reflective layer after which the transmitted light is partlyreflected by the partially reflective layer. The coefficient ofreflection of the transflective and partially reflective layer areapproximately equal to each other so that the two layers constitute aso-called Fabry-Perot interferometer. Dependent on the distance and themedium between the transflective layer and the partially reflectivelayer, interference occurs between the light reflected directly by thetransflective layer and the light reflected by the partially reflectivelayer. The transflective and partially reflective layers are provided onopposite sides of a piezo-electric crystal. The distance between thetransflective and reflective layer is controlled by means of a voltageprovided across the layers so that the thickness of the piezo-electriccrystal varies to a greater or lesser extent. The construction andcontrol of such a device, however, are not suitable for use in a displaydevice in which the picture is constructed from a large number ofindividually controllable display elements.

It is therefore the object of the invention to provide a display devicewhich can be constructed in a simple manner by means of a large numberof display elements.

A further object of the invention is to provide a display device whichis suitable for displaying alphanumerical and video information.

Still a further object of the invention is to provide a display devicewhich can be both voltage-controlled and charge-controlled.

Still another object of the invention is to provide a display devicewith which information can be observed in colour.

For that purpose, according to the invention, a display device of a kindmentioned in the opening paragraph is characterized in that thepartially reflective layer constitutes a pattern of resilientlyconnected electrodes and the transflective layer is divided into regionswhich are common for one or more resiliently connected electrodes.

An embodiment of a display device of the invention, which can beconstructed as a so-called crossbar display, is characterized in thatthe pattern of resiliently connected electrodes constitutes a first gridof parallel strips and the common regions of the transflective layerconstitute a second grid of parallel strips which cross the strips ofthe first grid.

A further embodiment of a display device of the invention ischaracterized in that the pattern of resiliently connected electrodesconstitutes a first set of electrodes and the regions of thetransflective layer constitute a second set of electrodes. By applying avoltage across the electrodes of the first set and the electrodes of thesecond set, a resiliently connected electrode of the first set isattracted to an electrode of the transflective layer as a result ofelectrostatic force, which movement, however, is counteracted by theresilience of the resiliently connected electrode. Below a given voltagedependent on the distance between the electrodes a stable equilibriumoccurs between the electrostatic force and the resilience so that over acertain region of the electrode distance the distance between aresilient electrode and an electrode of the transflective layer can beadjusted. At larger values of the voltage the equilibrium between theelectrostatic force and the resilience becomes unstable so that theresiliently connected electrode is accelerated towards the electrode ofthe transflective layer.

Still a further embodiment of a display device of the invention ischaracterized in that the pattern of resiliently connected electrodesconstitutes a first set of electrodes and a second supporting platewhich is provided with a set of electrodes in registration with theregions of the transflective layer is spaced apart from the firstsupporting plate. The distance between a resiliently connected electrodeand a region of the transflective layer is varied by applying a voltageacross an electrode of the second supporting plate and a resilientlyconnected electrode. Since the distance between the second supportingplate and the partially reflective layer of the resiliently connectedelectrodes can be chosen to be larger than the distance between thefirst supporting plate and the partially reflective layer of resilientelectrodes, the range within which a stable equilibrium occurs betweenthe electrostatic force and the resilience is larger than in theabove-described previous embodiment. As a result of this, forcontrolling the observed reflection between maximum and minimumintensity, zero order effects may be used. The advantage of this is thatthe angle independence of the observed phenomena is large.

Again another embodiment in which the electrodes of the first set areinterconnected and the electrodes of the second set are strip-shaped ischaracterized in that a second supporting plate is provided at somedistance from the first supporting plate and has a third set ofstrip-shaped electrodes which cross the strip-shaped electrodes of thesecond set. By applying suitable voltages across electrodes of thefirst, second and third sets, the resiliently connected electrodes mayengage either the first supporting plate or the second supporting plate.It is to be noted that a display device having two supporting platesprovided with electrodes and having resiliently connected electrodesbetween the supporting plates is known per se from Netherlands patentapplication No. 7510103. This Application, however, deals with aliquid-filled display device, while the distance between the supportingplates is much larger than the small distance between the supportingplates required for interference in a display device according to theinvention.

Another embodiment of a display device is characterized in that thedisplay device comprises means to provide charge on the resilientelectrodes. The control of the display device by means of charge has theadvantage that throughout the distance between a resiliently connectedelectrode and an electrode of the transflective layer the electrostaticforce occurring as a result of the charging can be in equilibrium withthe resilience of a resiliently connected electrode.

A further embodiment of a charge control display device is characterizedin that the first supporting plate forms part of a glass envelope whichcomprises an electron gun to generate an electron beam directed onto thefirst supporting plate, which electron beam scans the first supportingplate according to a regular pattern and charges the resilientlyconnected electrodes. The resilient electrodes are provided with thedesired charge by modulating the electron beam is known manner inaccordance with the presented information.

Such a display device is suitable for a data processing device whichcomprises a light source, first optical means to obtain a parallel lightbeam which is incident on the display device, which dispaly devicemodulates the incident light.

Coloured pictures can be obtained by using a light source which emitsred, green and blue light.

Such a display device is particularly suitable for a projectiontelevision device which has at least two display devices, each of whichdisplay devices comprises a light source which emits light of onecolour, first optical means to obtain a parallel light beam which isincident on the display device which modulates the incident light, andsecond optical means to project the modulated light on a screen which iscommon for the display devices. Each display device is used to modulatelight of one colour, the pictures of the display devices being projectedon a screen so as to be overlapping so that a coloured picture isobserved.

It is to be noted that a projection television device is disclosed inU.S. Pat. No. 3,746,911 in which mirrors, which can be deformed, arecharged by means of an electron beam. Dependent on the charge, themirrors are curved more or less. The reflected light is displayed on ascreen by means of a Schlieren optical system.

In such a prior art projection television device, however, annoyingdiffraction patterns occur which are caused by the gaps between themirrors. Moreover, the required Schlieren optical system is acomplicated optical system since this is required to display thereflected light of the curved mirrors on the screen but is also requiredto block the reflected light of the non-curved mirrors.

A first method of manufacturing a display device according to theinvention is characterized by the following steps:

(a) providing a pattern of a transflective material on a supportingplate,

(b) providing a layer of aluminum which can be etched by means of afirst etchant,

(c) anodizing regions of the layer of aluminium which should remainconnected to the supporting plate,

(d) electro depositing a layer of an electrode material which can beetched by means of a second etchant,

(e) providing the electrode pattern in the layer of electrode materialby means of a photo-etching method and the second etchant,

(f) removing the non-anodized parts of the aluminium by the edges of thelayer of electrode material by means of the first etchant.

A second method of manufacturing a display device is characterized bythe following steps:

(a) providing a pattern of a transflective material on a supportingplate,

(b) providing a layer of aluminium which can be etched by means of afirst etchant,

(c) removing regions in the layer of aluminium by means of aphoto-etching method and the first etchant,

(d) electro depositing a layer of an electrode material which can beetched by means of a second etchant,

(e) providing an electrode pattern in the layer of electrode material bymeans of a photo-etching method and the second etchant,

(f) removing the layer of aluminium by the edges of the layer ofelectrode material by means of the first etchant.

In order to ensure the parallelism of the part of the resilientelectrode which is effective for display with the transflective layerand to make this independent of the actual resilient flexible parts ofthe resilient electrodes, according to a further embodiment of the firstor second method, the effective part of the resilient electrodes, afterstep e, is provided by electro deposition with a reinforcement layer ofelectrode material which can be etched by means of the second etchant.

In this manner it is possible to manufacture resiliently connectedelectrodes with a very large smoothness, which electrodes are present ata very short distance from the supporting plate substantially withoutmechanical stresses.

The invention will now be illustrated with reference to the accompanyingdrawing, of which

FIGS. 1a and 1b are diagrammatic drawings to illustrate the operatingprinciple of the display device,

FIG. 2 is a sectional view of a first embodiment of a display device,

FIG. 3 is a plan view of a resilient electrode,

FIGS. 4a and 4b illustrate the operation of the display device in thecase in which the display device is voltage-controlled,

FIG. 4c illustrates the operation of a modified display device inaccordance with the invention,

FIGS. 5a and 5b are sectional views of further embodiments of a displaydevice,

FIGS. 6a and 6b illustrate the operation of the display device in thecase in which the display device is charge-controlled,

FIG. 7a is a sectional view of a fourth embodiment of a display device,

FIG. 7b shows a detail of the display device of FIG. 7a,

FIG. 8 shows an embodiment of a device having a display device inaccordance with the invention,

FIG. 9 shows an embodiment of a projection television device inaccordance with the invention,

FIGS. 10a, b, c and d illustrate the methods of manufacturing a displaydevice in accordance with the invention.

The operating principle of a display device in accordance with theinvention will be explained with reference to FIG. 1a. Showndiagrammatically are a transflective layer 1 and a partially reflectivelayer 2 present at a distance d therefrom. The coefficient of reflectionof layer 1 and layer 2 is approximately the same. A part of an incidentlight beam 3 is reflected by the transflective layer 1 and a part istransmitted. The transmitted light is partially reflected by thepartially reflective layer 2. The light not reflected by the layer 2 canbe transmitted or be absorbed by the layer 2. By repeated internalreflections at the layers 1 and 2, a number of parallel partial beams5a, 5b and 5c are formed with decreasing intensity. When these parallelpartial beams 5 together have substantially the same intensity as thepartial beam 4 directly reflected at the layer 1, the intensity of thereflected light as a result of the occurring interference can becontrolled, by varying the distance d for a given wavelength, betweensubstantially 0 and a maximum value which depends on the reflectioncoefficient of the layers 1 and 2. When the incident light beam iscomposed of light of several wavelengths, reflected light of thesuccessive wavelengths is observed when the distance d is varied.

FIG. 1b shows the relative intensity φ of the total reflected light as afunction of the phase difference α determined by the distance betweenthe layers 1 and 2, between the light reflected directly at the layer 1and reflected at the layer 2, for a reflection coefficient of the layers1 and 2 of 0.5.

FIG. 2 is a diagrammatic sectional view of an embodiment of a displaydevice. A plurality of strip-shaped transflective electrodes 11 areprovided on a glass supporting plate 10. The electrodes 11 are formed bya 0.05 μm thick layer 12 of indium oxide or tin oxide on which a 0.01 to0.02 μm thick layer 13 of chromium is provided. Instead of the layers 12and 13, one layer only of chromium may be provided, if desired.Electrodes 14 are resiliently connected to pillars 15 at a distance of0.3 μm from the strip-shaped electrodes 11. The electrodes 14 areinterconnected in such manner that strip-shaped electrodes 16 are formedwhich are substantially at right angles to the strip-shaped electrodes11. In this manner a so-called cross-bar display is obtained in whichthe electrodes 11 constitute the columns and the electrodes 16constitute the rows of the display device. The resilient electrodes 14are manufactured from nickel and have a thickness of 0.3 μm. The pillars15 are manufactured from aluminium oxide. The pillars 15 may also bemanufactured from the layer of nickel of the resilient electrodesthemselves, which will be explained in detail with reference to FIG.10d.

FIG. 3 is a plan view of an individual resilient electrode 20. Eachelectrode 20 comprises a central portion 21 which by thin strips 23 issecured to the pillars 25 shown in broken lines by means of the pads 24.The strips 23 constitute resilient elements of the display element sothat the central portion 21 of the electrodes 20 can be moved parallelto itself in a direction perpendicular to the electrodes. The electrode20 has an area of 200×200 μm².

The operation of a resilient electrode will be explained in detail withreference to FIGS. 4a and 4b. FIG. 4a shows diagrammatically one displayelement in which a transflective electrode 31 is provided on a glasssupporting plate 30 and a resilient electrode 33 is provided at adistance a therefrom by means of the pillars 32. The resilient electrode33 may be represented as a central reinforced portion 34 which isconnected to the pads 35 by means of the springs 36 having a collectivespring constant C. When a voltage V is applied across the electrodes 31and 33 the central portion 34 experiences an electrostatic forcedirected towards electrode 31 and an oppositely directed resilience. Theelectrode 34 is in equilibrium when it holds that: ##EQU1## where x isthe displacement of the portion 34 and ε_(o) is the permittivity of thespace between electrodes 31 and 33.

In FIG. 4b, the above equation is shown as a plot of V against X. Forvoltages below ##EQU2## the equilibrium between the electrostatic forceand the resilience is stable. For voltages above V₁ the equilibriumbecomes labile and the electrode 34 flips towards electrode 31.

The display device can be operated in various ways. According to a firstway, the electrodes are controlled by voltages which are smaller than V₁so that the electrode 34 can move over a distance X=1/3a taken from theposition in which the electrode 34 is at a distance a from the electrode31 at a voltage V=0. When a light beam of wavelength λ₁ i.e. light ofone colour impinges on the display device, at an angle α to the normalof the first supporting plate and when the distance between theresilient electrode 33 and electrode 31 at V=0 is equal to a=(3/4)λ₁/cos α, then, by varying the distance over a range of 1/3a, thereflection of the incident light can be controlled from zero to maximumintensity. When the incident light beam comprises light of variouswavelengths, reflected light of the respective wavelengths and hencecolours are observed when varying the distance between the electrodes.It is also possible to use the bistable mode in which the resilientelectrode 34 can be only in two extreme positions. For this purpose anembodiment slightly varied with respect to FIG. 4a is necessary as shownin FIG. 4c, in which corresponding components are referred to by thesame reference numerals. At a voltage V=0 the electrode 34 is at adistance a from the electrode 31. This distance a has been chosen sothat maximum reflection occurs for light of a wavelength λ₁ incident atan angle α. At a voltage exceeding V₁ the resilient electrode 34 flipsto electrode 31. In order to prevent short-circuit, the electrode 31 hasa number of insulating pillars 37 the height of which has been chosen tobe so that when the electrode 34 engages the pillars 37 the distancebetween the resilient electrode 34 and electrode 31 is just equal to thedistance for which the reflection of the incident light beam is zero.When an incident light beam is used having light of two wavelengths, theextreme positions of the resilient electrode 33 can be chosen to be sothat in one position the reflection of light of the first wavelength andin the other position reflection of light of the second wavelength ismaximum. It is also possible to use the display device with ambientlight. When the angle at which the display device is observed is varied,the wavelength and hence the colour of the reflected light will vary,but the contrast of the observed picture is maintained.

FIG. 5a is a sectional view of another embodiment of a display device. Anumber of strip-shaped transflective regions 41 are provided on a glasssupporting plate 40. A plurality of resilient electrodes 42 is providedat a distance a from the regions 41 by means of pillars 43. Theresilient electrodes 42 are interconnected and constitute strip-shapedelectrodes which cross the strip-shaped regions 41. Spaced apart fromthe first supporting plate 40 is a second supporting plate 44 which issupported by a frame 45. A number of strip-shaped electrodes 46 areprovided on the supporting plate 44 so as to be in registration with thestrip-shaped regions 41 on the supporting plate 40 and which are at adistance b from the resilient electrodes 42. The distance between theresilient electrodes 42 and the strip-shaped transflective regions 41 isvaried by applying a voltage across the resilient electrodes 42 and thestrip-shaped electrodes 46 on the second supporting plate 44. Thisembodiment has the advantage that the resilient electrodes 42 can bedriven over a large range. The distance b between the electrodes 46 andthe resilient electrodes 42 can as a matter of fact be chosen to belarger than the distance a between the resilient electrodes 42 and thestrip-shaped transflective regions 41. The distance of 1/3b over whichthe resilience is in stable equilibrium with the electrostatic forcethus is larger than the distance 1/3a as is the case in the FIG. 2embodiment.

In the FIG. 2 embodiment it is not possible in the case of voltagecontrol to use the zero order maximum in the intensity of the reflectedlight since the displacement of the resilient electrode over a distance1/3a is not sufficient to make the distance between the resilientelectrode and the transflective layer equal to the distance for whichthe reflection of the light is equal to zero. In the present embodiment,due to the larger distance 1/3b over which the resilient electrode canbe moved it is possible, starting from the zero order maximum to movethe resilient electrode so that the reflection of the light is equal tozero. The use of zero order effects has the advantage that the picturecan be observed at a large angle in contrast with higher order effectswhere, upon variation of the angle at which the image is observed,successively maximum reflection and no reflection is observed. Thedistance a is, for example, 0.05 μm and the distance b is, for example,10 μm, so that the maximum distance between the resilient electrodes 42and the strip-shaped regions 41 is substantially 3 μm.

FIG. 5b is a sectional view of a further embodiment of a display device.Corresponding components are referred to by the same reference numeralsas in FIG. 5a. A number of strip-shaped electrodes 46 are provided onthe supporting plate 44 and intersect the strip-shaped electrodes 41 atright angles. A number of pillars 47 of insulating material are providedon the electrodes 41 and 46. As is known per se from Netherlands patentapplication No. 7510103 the device is bistable, that is to say theresilient electrodes 42 may be only in two extreme positions. Byapplying suitable voltages across the electrodes 41, 42 and 46, theresilient electrodes 42 may engage either the pillars 47 on electrodes41 or pillars 47 on electrodes 46. The height of the pillars 47 ischosen to be so that, for example, with an incident light beam of twowavelengths in one extreme position of the resilient electrode thereflection of the light of the first wavelength is maximum and in theother extreme position the reflection of the light of the secondwavelength is maximum. It is also possible to use the display devicewith ambient light.

The operating principle of a further embodiment of the display devicewill be explained with reference to FIGS. 6a and 6b. Only one displayelement is shown diagrammatically. A transflective electrode 51 isprovided on a glass supporting plate 50. A resilient electrode 52 whichmay be represented by a central reinforced portion 53 which is connectedto pads 54 by means of springs 55 is provided at a distance a from theelectrode 51 by means of pillars 56. The resilient electrode 53 ischarged by means of an electron beam 57. As a result of a charge Qelectrode 53 experiences an electrostatic force F_(e) =(Q2/2ε₀ A), whereA is the area of the electrode 53. From this formula it appears that theforce is proportional to the square of the charge and is independent ofthe distance between the resilient electrode 53 and the electrode 51. Asa result of the electrostatic force electrode 53 also experiences anoppositely directed resilience F_(v) =CX, where C is the collectivespring constant of the springs 55 and X is the displacement of theelectrode 53.

FIG. 6b shows how the displacement of the resilient electrode 53 dependson the charge Q provided by the electron beam 57. From this it appearsthat when the resilient electrode 53 and the electrode 51 are separatedby any amount between 0 and a the electrostatic force is in stableequilibrium with the resilience so that the electron 53 can be drivenover the whole distance a.

FIG. 7a shows a practical embodiment of a display device in which theresilient electrodes are charged by means of an electron beam. A glassenvelope 60 comprises a display window 61, a cone 62 and a neck portion63. On the inside of the display window 61 a matrix of display elements64 is provided. An electron gun 65 to generate an electron beam 66 isprovided in the neck 63. The electron gun 65 may be of any knownconstruction and needs no further explanation. By means of a system ofdeflection coils 67 placed around the glass envelope the electron beam66 is deflected, the matrix 64 of display elements being scannedaccording to a frame of parallel lines. The electron beam 66 ismodulated in known manner with the presented video information. In thismanner the individual picture elements are provided with a charge as aresult of which the resilient electrodes are attracted to a greater orlesser extent to the fixed common electrode on the display window 61which is earthed.

For displaying motion television pictures the display window should bescanned as a whole by the electron beam 25 times per second. The chargeon each of the resilient electrodes should therefore leak away inapproximately 1/25 sec. This relaxation time of the resilient electrodeis produced by connecting the resilient electrodes via a resistor to theearthed electrode on the display window.

FIG. 7b is a perspective view of a manner in which this can be realized.A resilient electrode 64 is spaced apart from the display window 61 bymeans of a pillar 69. An electrode 68 insulated from the pillar 69 isprovided on the display window and is earthed. The resilient electrode64 is connected to the electrode 68 via the resistor 70 so that thecharge on the resilient electrode 64 can leak away in a certain periodof time via the pillars 69 and resistors 70.

Such a display device is suitable for use in a data processing device(data display). FIG. 8 shows an embodiment of such a device. Referencenumeral 75 is a display device as shown in FIG. 7a. The display window76 of the display device 75 is illuminated uniformly at a given angle bya light source 77 which is placed at the focal point of a parabolicmirror 78. The spectrum of the light emitted by the light source 77comprises three narrow bands around the wavelengths λ₁ =0.6 μm (red), λ₂=0.54 μm (green) and λ₃ =0.45 μm (blue). Dependent on the distancebetween the resilient electrodes and the electrodes on the displaywindow which is determined by the quantity of charge which the electronbeam deposits on the resilient electrodes in accordance with thepresented information, light of a given wavelength and hence colour isreflected. Herewith it is possible, for example, to display colouredletters against a differently coloured background. A bright colourpicture the brightness of which is determined for the greater part bythe intensity of the light beam incident on the display screen isobserved by an observer 79.

FIG. 9 is a plan view of an embodiment of a projection television devicein accordance with the invention. The device comprises three displaydevices 80, 81 and 82. Three light sources 83, 84 and 85 which areplaced at the focal points of parabolic mirrors 86, 87 and 88, ensurethat a parallel light beam is incident on each of the display devices80, 81 and 82.

The light sources 83, 84 and 85 emit red, green and blue light,respectively, so that red, green and blue pictures, respectively, arereflected by the display devices 80, 81 and 82. The three mono-colouredpictures are projected on the screen 92 by means of the lenses 89, 90and 91 in such manner that the three pictures overlap each other. Acoloured picture is observed on the screen.

An embodiment of a method of manufacturing a display device will beexplained with reference to FIG. 10. FIG. 10a shows a glass supportingplate 100 on which a pattern 101 of chromium is vapour-deposited in athickness of 0.01 to 0.02 μm. A 0.4 μm thick aluminium layer 102 is isprovided across it. A layer 103 of a photolacquer is then provided onthe aluminium layer 102. Apertures 104 are provided in the layer 103 inknown manner. The apertures 104 correspond to the areas in the aluminiumlayer 102 which should remain connected to the supporting plate 100. Atthe area of the apertures 104 the aluminium is then anodized after whichthe layer 103 is removed. These anodized regions are denoted in FIG. 10bby reference numeral 105. A nickel layer 106 in a thickness of 0.15 μmis provided on the aluminium layer 102. The nickel layer 106 is providedby electroplating the layer from a nickel sulphanate bath. As a resultof this a nickel layer is obtained which engages the aluminium layer 102substantially without mechanical stresses. By means of a knownphotoetching method the shape of the resilient electrode as shown inFIG. 3 is etched in the layer 106. The etchant is nitric acid which doesnot attack the underlying aluminium layer 102 and the anodized regions105. In order to ensure the parallelism of the central parts of theresilient electrodes (see FIG. 3) with the electrodes 101 and to make itindependent of the actual resilient flexible parts of the electrodes,the central portions of the resilient electrodes are provided with areinforcing layer 107 of Ni or Ag which is provided by electroplating.Etching with concentrated H₃ PO₄ at 60° C. is then carried out whichdoes not attack the nickel layer 106 and the anodized regions 104 butdoes attack the aluminium layer 102. The aluminium layer 102 is removedby so-called "underetching" by the edges of the electrodes, after whichthe construction shown in FIG. 10c is obtained. According to a secondembodiment of a method of manufacturing a display device, the aluminiumin the stage shown in FIG. 10a is not anodized but etched away at thearea of the apertures 104. The nickel layer 106 is then provided whichnow also covers the walls of the apertures in the aluminium layer 102.FIG. 10d shows the result hereof. The resilient electrodes are kept at adistance from the supporting plate 100 by nickel pillars. The methodcontinues in the same manner as the first embodiment. The flatness ofthe resilient electrodes is particularly good due to the electroplatingof the layer 107. The distance between resilient electrodes and thetransflective regions 101 can be determined with very great accuracy bymeans of the thickness of the layer of vapour-deposited aluminium.

What is claimed is:
 1. A display device comprisinga transparent firstsupporting plate, a partially reflective layer separately spaced fromand relatively movable to said first plate to promote opticalinterference, a pattern of a plurality of resiliently connectedelectrodes of said partially reflective layer, and a plurality oftransflective regions on said supporting plate, said transflectiveregions being spaced from and common for at least one of saidresiliently connected electrodes, and said partially reflective layerreflecting to substantially the same extent as said transflectiveregions.
 2. A display device according to claim 1, wherein said patternof resiliently connected electrodes constitutes a first grid of parallelstrips, and wherein said plurality of transflective regions constitutesa second grid of parallel strips crossing said first grid of parallelstrips.
 3. A display device according to claim 1, wherein said patternof resiliently connected electrodes constitutes a first set ofelectrodes, and said plurality of transflective regions constitutes asecond set of electrodes.
 4. A display device according to claim 3,wherein means are provided for forming charge on said first set ofelectrodes
 5. A display device according to claim 4, further comprisinga light source and first optical means for obtaining a parallel lightbeam incident on said display device, said display device modulatingsaid incident light, wherein a data processing device is provided.
 6. Adisplay device according to claim 4, further comprising at least asecond said display device, each of said display devices being providedwith a light source emitting light of a single color, first opticalmeans for providing a parallel light beam incident on said displaydevice, said display device modulating said incident light, and secondoptical means for projecting said modulated light onto a screen commonto all display devices, wherein a projection television device isprovided.
 7. A display device according to claim 3, wherein said patternof resiliently connected electrodes constitutes a first grid of parallelstrips, and wherein said plurality of transflective regions constitutesa second grid of parallel strips crossing said first grid of parallelstrips.
 8. A display device according to claim 1, wherein said patternof resiliently connected electrodes constitutes a first set ofelectrodes and wherein a second supporting plate provided with a furtherset of electrodes in registration with said plurality of transflectiveregions is spaced from said first supporting plate.
 9. A display deviceaccording to claim 8, wherein said pattern of resiliently connectedelectrodes constitutes a first grid of parallel strips, and wherein saidplurality of transflective regions constitutes a second grid of parallelstrips crossing said first grid of parallel strips.
 10. A display deviceaccording to claim 1, wherein means are provided for forming charge onsaid resilently connected electrodes.
 11. A display device according toclaim 10, further comprising a light source and first optical means forobtaining a parallel light beam incident on said display device, saiddisplay device modulating said incident light, wherein a data processingdevice is provided.
 12. A display device according to claim 10, furthercomprising at least a second said display device, each of said displaydevices being provided with a light source emitting light of a singlecolor, first optical means for providing a parallel light beam incidenton said display device, said display device modulating said incidentlight, and second optical means for projecting said modulated light ontoa screen common to all display devices, wherein a projection televisiondevice is provided.
 13. A display device according to claim 10, whereinsaid pattern of resiliently connected electrodes constitutes a firstgrid of parallel strips, and wherein said plurality of transflectiveregions constitutes a second grid of parallel strips crossing said firstgrid of parallel strips.
 14. A display device comprisinga transparentfirst supporting plate, a partially reflective layer spaced from andrelatively movable to said first plate to promote optical interference,a pattern of resiliently connected electrodes of said partiallyreflective layer constituting a first set of electrodes, and a pluralityof transflective regions on said first supporting plate constituting asecond set of electrodes, said transflective regions being common for atleast one of said resiliently connected electrodes, and said partiallyreflective layer reflecting to substantially the same extent as saidtransflective regions, wherein electrodes of said first set areinterconnected and electrodes of said second set are strip-shaped, andwherein a second supporting plate is spaced from said first supportingplate, said second supporting plate having a third set of electrodeswhich are strip-shaped and cross said strip-shaped electrodes of saidsecond set.
 15. A display device according to claim 14, wherein saidpattern of resiliently connected electrodes constitutes a first grid ofparallel strips, and wherein said plurality of transflective regionsconstitutes a second grid of parallel strips crossing said first grid ofparallel strips.
 16. A display device comprisinga transparent firstsupporting plate, a partially reflective layer spaced from andrelatively movable to said first plate to promote optical interference,a pattern of resiliently connected electrodes on said partiallyreflective layer constituting a first set of electrodes, a plurality oftransflective regions on said first supporting plate constituting asecond set of electrodes, said transflective regions being common for atleast one of said resilently connected electrodes, and said partiallyreflective layer reflecting to substantially the same extent as saidtransflective regions, and means for forming charge on said first set ofelectrodes, wherein said first supporting plate is formed of a glassenvelope, and wherein said means includes an electron gun generating anelectron beam onto said first supporting plate, said electron gunscanning said electron beam over said first supporting plate in aregular pattern to form charge on said first set of electrodes.
 17. Adisplay device according to claim 16, further comprising a light sourceand first optical means for obtaining a parallel light beam incident onsaid display device, said display device modulating said incident light,wherein a data processing device is provided.
 18. A display deviceaccording to claim 16, further comprising at least a second said displaydevice, each of said display devices being provided with a light sourceemitting light of a single color, first optical means for providing aparallel light beam incident on said display device, said display devicemodulating said incident light, and second optical means for projectingsaid modulated light onto a screen common to all said display devices,wherein a projection television device is provided.
 19. A display devicecomprisinga transparent first supporting plate, a partially reflectivelayer spaced from and relatively movable to said first plate to promoteoptical interference, a pattern of resiliently connected electrodes ofsaid partially reflective layer, a plurality of transflective regions onsaid first supporting plate, said transflective regions being common forat least one of said resiliently connected electrodes, and saidpartially reflective layer reflecting to substantially the same extentas said transflective regions, and means for forming charge on saidresiliently connected electrodes, wherein said first supporting plate isformed of a glass envelope, and wherein said means includes an electrongun generating an electron beam onto said first supporting plate, saidelectron gun scanning said electron beam over said first supportingplate in a regular pattern to form charge on said resiliently connectedelectrodes.
 20. A display device according to claim 19, furthercomprising a light source and first optical means for obtaining aparallel light beam incident on said display device, said display devicemodulating said incident light, wherein a data processing device isprovided.
 21. A display device according to claim 19, further comprisingat least a second said display device, each of said display devicesbeing provided with a light source emitting light of a single color,first optical means for providing a parallel light beam incident on saiddisplay device, said display device modulating said incident light, andsecond optical means for projecting said modulated light onto a screencommon to all said display devices, wherein a projection televisiondevice is provided.